Ответ:
100 − 50 = 50; 20 + 40 = 60; 30 + 70 = 100; 60 − 40 = 20; 50 − 40 = 10; 80 − 70 = 10; 50 − 30 = 20; 60 − 40 = 20; 40 + 50 = 90; 90 − 70 = 20.
100 − 50 = 50; 20 + 40 = 60; 30 + 70 = 100; 60 − 40 = 20; 50 − 40 = 10; 80 − 70 = 10; 50 − 30 = 20; 60 − 40 = 20; 40 + 50 = 90; 90 − 70 = 20.